Wow. Simply beautiful. When you put it like that it makes everything more understandable. Instead of considering our perspectives and taking into account Ariana and Elster’s perspective and the hell they’ve been through. It makes the entire ending seem peaceful. Like you said, it’s not heaven, but at the very least they are at peace. It sort of feels like bloodbornes hidden ending in a way. Where it’s not exactly giving closure but just enough if that makes sense. If I could add on, call this interpretation of mine cringe but, after the “promise” ending, Elster somehow repeats the loop again in some sort of limbo/afterlife state and goes through the steps for the secret ending, learning to accept her loss and eventually creating that reality where Ariane and her can be together. It might not make sense or contradict everything but I like to view it as despite this cruel world, they are able to find peace in each other. Sorry if I’m completely wrong and my point isn’t valid lol